Darkness-Induced Audience Apathy: See main entry for details. Brief recap: the 3e and early 4e sig characters were largely antiheroes. 4e's later sig characters were rapists, vivisectionists, spree killers (who in 3e were specifically held up as examples of bad shadowrunning), and amoral assassins. There are no good MegaCorps (or factions with enough power to stand to them), period. Oh, and FastJack, grand old dean of shadowrunning, is now starting to go senile, though this turned out to be a Red Herring. 5e has taken steps to come back from this... except, you know, Deus reappearing and the freaking Elder Gods, pure Lovecraft-level bad shit, seemingly taking an interest on Earth.
Lampshaded in Dark Terrors:
Slamm-0!: For once, I would love a nice, quiet JackPoint evening where the world doesnt seem to be ending every Thursday.
Beating this trope senseless and leaving it in an alley is the point of 5e book Better Than Bad, a guide to how to model social change for the better, as well as amplifying it through shadowrunning. The book also reveals Harlequin's alive and back to playing Trickster Mentor for characters who actually want to save some portion of the world.
Game-Breaker/Elite Tweak: Third Edition has an Edge called "Connected" that, when taken for a vendor contact, allows you to buy from that contact at the list price or sell at the street price, which can be as much as three times more. Thus, taking that edge for two contacts (one to buy from, one to sell to) allows a player to get ridiculous amounts of money while the GM isn't paying attention.
A troll adept, with only three points of Magic and the right skills in 4th Edition rulebooks, could pick up a paperclip and explode someone's head by throwing it really hard.
The physical adept can become noticeably broken if you use initiation to offset the Essence cost of cyberware or to avoid focus addiction.
The chemical DMSO. If you splash it on someone, it allows for other chemicals to be absorbed into the DMSO-coated skin. Unless your armor is waterproof, you're in a world of trouble - if whatever goodies your assailant used in the cocktail don't ruin your day, everyday contaminants will. The end result being that if you mix DMSO with poisonous drugs and load it into a squirt gun, you get a super soaker that deals one-hit kills. You can hear details about how this can affect a game environment in this video.
Truth in Gaming - DMSO does precisely that. Luckily, IRL no-one's figured out how to make a squirt gun safe to use with said payload; one mistake and the shooter gets a handful and thus a bloodstream-ful of whatever they're spraying. On top of that, the reason it's not more prevalent in reality is because it doesn't just carry a payload; it makes the skin permeable to chemicals that are already present prior to exposure, and takes a while to wear off - someone can take a DMSO splash and be susceptible to environmental hazards hours later.
Spellcasters have always been pretty powerful but 5e's Mystic Adept has gone from an unfortunate exception to that rule to a near Master of All thanks to their Adept powers no longer lowering their Magic stat. They don't have an innate Astral Perception compared to other spellcasters but Adept powers can fix that.
Quickening in 5E. What keeps spellcasting in Shadowrun from the way it's used in Dungeons and Dragons is that spellcasters take cumulative -2 penalty to all checks for each buff they have to concentrate on. With a low-karma investment and a spellcasting friend with at least one level of initiation, however, you can quicken a spell, i.e render it permanent. Quickened spells can be dispelled or blocked by mana barriers, but they have a permanent bonus equal to their force to resist dispels and punch through barriers. If you have a contact with access to Quickening or, gods forbid, your spellcaster learns how to do it, the low-end way to apply it is for your party to have their stats increased by six and get three extra initiative die for a handful of karma and an evening's work.
Genius Bonus: The Crime Mall is a literal Black Market complex operating from the remains of an actually abandoned shopping mall in the Puyallup Barrens, dealing with goods that normally couldn't be found and/or purchased from regular merchants or are considerably beyond the reach of anybody who has a SIN. The real life Puyallup town has its origins stemming from Native American tribes who first settled there in around the 1830s and whose name literally means "the generous people" in their native dialect. It was only after 1877 that a European cartographer mapped the town and named it after the tribes who lived there.
The Shadowbeat supplement from 1992 reveals that American football is alive and well in the 2050s, with many of the old NFL teams still operating under the same names... well, except for the Washington Chieftains. Even with the hostility between the old U.S. and the Native Americans that became independent, somebody decided that "Redskins" was just a bit inappropriate.
The Paranormal Creatures of North America sourcebook made a joking reference to Arnold Schwarzenegger having gone into politics, over a decade before he ran for governor of California.
The Universal Brotherhood sourcebook describes a thinly veiled expy of Scientology. Just replace the "nuked ghost" thing with insect spirits. Hilariously, it was released in 1990, almost a full decade before Scientology became widely known as an Acceptable Target and displays considerably more subtle knowledge of said religion than most modern digs at it - specifically its claims of having "an owner's manual for the human mind."
At the time, that quote was the actual TV marketing blurb for Dianetics.
In Nigel Findley's Shadowplay, a decker gets a hold of some Lost Technology - the ability to tap what was thought to be 100% secure fiber-optic communications. Global war nearly breaks out as everyone and their dog wants to be the sole owner of the technology. She ultimately posts it on the Corporate Court's message board so everyone has it, making the fighting pointless. Hilarious part? She had to fight her way past the 2050's equivalent of the NSA in order to do it, as the American government would prefer global war to losing any of their surveillance capability.
Saeder-Krupp is a fictional amalgation of Krupp Heavy Industries with the fictional Saeder Munitions. Real Life Krupp Heavy Industries merged with Thyssen AG in 1999, forming the ThyssenKrupp Mega-Corp as a result.
Tear Jerker: Toward the end of Hard Targets, Clockwork gets hit by an IC after Glitch shuts down a long argument. Bull asks Slamm-O! why he wasn't laughing like an idiot. His response?
Slamm-O! It's times like this I wish we still had 'Jack around to give his two cents.
What an Idiot!: In one of the snippets from Forbidden Arcana, Lyran advertised that she'd made out with a bunch of reagents from the Great Dragon Hestaby's lair after the latter's exile and tried to sell them on Jackpoint. She completely forgot that Hestaby has an account there. (Nothing serious came of it, fortunately for Lyran.)
Tar Pit ice in matrix runs, a hidden secondary ice which will erase whichever program you're using if it fails and up the alarm rating to Red. Since Deception and Attack are basically the only two programs you'll ever use, this has a 50/50 chance of forcing you to abort a run entirely. Even if you grind up your Decking score to max and have a fully-upgraded deck, chances are good you'll trigger it. Keeping weak programs as a sacrifice is pretty much the only reliable way to keep on moving through the high end systems. If you get hit by it while fighting Black Ice, pray you have a secondary attack program.
Hell Hounds in the real world. They travel in packs, move extremely fast, and hit like a ton of bricks. Until you get high end armor and weapons, an encounter with them spells death for you.
There's a shop in downtown Seattle that will buy stolen data. This is easily the most profitable activity in the entire game, enabling you to quickly upgrade your deck to steal larger and more valuable files, in addition to making it trivially easy to obtain all the best equipment and buy every contact. To give an example of just how broken it is, a single-run on a high-end system will near-certainly net you three times more cash than a shadowrun from even the most well-paying client, and that's at a minimum. A single file from the big corporations can be worth three times as much as a single shadowrun, sometimes even more. You can even do it in tandem with a hacking shadowrun to get the karma payout in addition to the money.
Even better: there's a terminal right next to the data purchaser's entrance. One could spend quite a bit of time just raiding random systems and selling the files off with maybe a quick break to take out any random attackers that pop up now and then. The best part is that the values of each file you find are apparently random: that 20Mp file you grabbed from a System Files datastore could easily be worth 5k nuyen.
The two programs that you can get from contacts — Degrade and Rebound — start broken. Degrade drops a node's rating to a minimum of 2. Used in tandem with Rebound, however, and even high-level systems become a joke: Rebound to set up defense while Degrade makes the node more manageable. This can also help with the Tar Pit, above: degrade the node a couple times and chances are remote your attack programs will be eaten.